Self-assembly of materials can be defined as the spontaneous organization of materials into ordered patterns without the need for human interference. Examples of material self-assembly range from snowflakes to seashells to sand dunes, all of which form some type of regular or ordered patterns in response to the external conditions.
Among various self-assembling materials, self-assembling block copolymers have attracted attention. Each self-assembling block copolymer typically contains two or more different polymeric block components that are immiscible with one another. Under suitable conditions, the two or more immiscible polymeric block components separate into two or more different phases on a nanometer scale and thereby form ordered patterns of isolated nano-sized structural units.
Such ordered patterns of isolated nano-sized structural units formed by the self-assembling block copolymers may potentially be used for fabricating periodic nano-scale structural units and therefore have promising applications in semiconductor, optical, and magnetic devices. Specifically, dimensions of the structural units so formed are typically in the range of 10 nm, which are extremely difficult to define using the conventional lithographic techniques. Further, the block copolymers are compatible with conventional semiconductor, optical, and magnetic processes, and structural units formed by the block copolymers can therefore be readily integrated into semiconductor, optical, and magnetic devices.
Most potential applications of the self-assembled block copolymer patterns require such patterns to be aligned in a predetermined direction and to be essentially free of defects. There is therefore a continuing need for improving the alignment of the self-assembled patterns of block copolymers and for reducing defects in such patterns.